Temperature responsive control device



Aug. 3, 1948.

R. A; 'WITTMANN TEMPERATURE RESPONSIVE CONTROL DEVICE Filed Feb.- 19,1945 a m a s y a My pagma Aug. 3, 1948 2,446,353

UNITED STATES PATENT' OFFICE 2,446,353 TEMPERATURE RESPONSIVE CONTROLDEVICE Robert A. Wittmann, Chicago, 111., assignor to E. B. MathewsonCo., Chicago, 111., a corporation of Illinois Application February 19,1945, Serial No. 578,689

- 7 Claims. (Cl. 175-336) The present invention relates to a novel meansof producing a mechanical movement by employing a magnetic field with aCurie point armature to bridge a gap in the field until the armature isheated above its Curie point and then employing the magnetic field toattract another armature into the magnetic field.

It is also the purpose of this invention to provide means to apply thelines of force of a magnet to hold a Curie point armature in a givenposition and to utilize the magnetic fiux of the magnet to drive theCurie point armature away from the place where it was held with anincreasing force when the Curie point armature has been heated throughits Curie point temperature.

It is also a purpose of this invention to provide means whereby themagnetic lines of force of a magnet are utilized efliciently to hold aCurie point armature in one position where the armature is a part of thepath of the magnetic lines of force until the armature has been heatedthrough its Curie point temperature, then to drive the armature to a newposition where the magnetic lines or force are not so attractive to itbut may still attract it when the armature has cooled below its Curiepoint temperature and is again in a ferromagnetic state, and holdingarmature by means of magnetic lines of force against return to itsoriginal position except by means of application of external force.

It is well known that there are many metals and alloys havingferromagnetic properties to varying degrees. These metals and alloys mayor may not contain iron. Upon heating one of these metals or alloyswhich has ferromagnetic properties a temperature is reached at which itsferromagnetic properties disappear. This. temperature is technicallyknown as the Curie point of the metal or alloy. When the metal or alloyis at a temperature above its Curie point it is often said tobeparamagnetic since it does not possess the ferromagnetic propertieswhich it has at ordinary i temperatures. Upon cooling a material in theparamagnetic condition it will regain its ferromagnetic properties. Itis possible to obtain a wide range of desired Curie point temperaturesby the proper selection and alloying of materials. See the examplesstated in my Patents 2,232,501 and 2,232,502. This enables one toutilize the material in. various ways for control means responsive totemperature conditions, regardless of or has heat generated therein byphysical or chemical action. The manner in which the Curie pointmaterial is heated or cooled is immaterial to the present invention. Myinvention concerns itself with the utilization of magnetic lines offorce in combination with the Curie point material to produce a controloperation manifested as a comparatively powerful movement of the controlarmature with respect to the magnetic lines of force with or withoutnecessitating subsequent replacement by an exterior force.

The nature and advantages of my invention will appear more fully fromthe following description and the accompanying drawings wherein a singleembodiment of the invention is shown. It is to be understood, however,that the drawings and description are illustrative only and that theyshould not be taken as limiting the scope of the invention exceptinsofar as it is limited by the claims.

In the drawings:

Figure 1 is a fragmentary plan view of a device embodying my invention;

Figure 2 is a sectional view taken on the line 2-2 of Figure 1;

Figure 3 is a fragmentary sectional view taken on the line 3-3 of Figure2; and

Figure 4 is a fragmentary sectional view of a modification of theconstruction shown in Figures 1 to 3 inclusive.

Referring now to the drawings, the present invention utilizes a magnetIn which may be either an electromagnet or a permanent magnet. Thismagnet for the specific construction shown is preferably ring shaped,but may be of any other suitable shape. A suitable material for a deviceof this character is a permanent magnet of an alloy which retains itscharacteristics as a permanent magnet over a long period of time withlittle decrease after an initial aging period. The north like materialmaking a tight joint M with the how the temperature is produced. Thusone may apply the temperature to a Curie point material by friction, byelectrical current, by fiame, or by conduction from a fiuid or gas whichcarries heat magnet. The ring [5 is threaded by threads I! to receive acylinder l 6 which is also of alike material. A suitable material forthe parts l2, l5 andli is a substantially pure iron. Alloyed ma- 3terials having desirable magnetic properties are also used. The cylinderl6 has its upper end flanged outwardly to provide a portion l8 that isaligned with the portion l3 but separated therefrom by a gap IS.

The structure thus far described provides a relatively large magnet IIIof high magnetic strength with a construction that concentrates anddirects the magnetic lines of force with a minimum loss to the smallannular gap I9. I utilize the high concentration of magnetic lines offorce at the gap I3 for effecting the desired mechanical movement.

On one side of the gap there is a ring 20 made of a Curie point metal ofrelatively low Curie point temperature, for example, a metal, the Curiepoint of which is approximately 152 F. The ring 20 is adapted to bethermally coupled to the control device, that is to say, the ring 20 isresponsive to a heat condition of a bearing, an electrical resistance,or some other heat producing means. For the sake of illustration, thering 20 is shown as being heated by. a heating coil 2|, the terminals ofwhich are connected to a suitable source of electrical current.

The mounting of the ring 20 comprises a plunger 24 of non-magneticmaterial extending through a bore 25 of the cylinder l6. This plungerhas a pin 33 mounted in it, and there are two vertical slots 3| and 3-2throughthe core [6 for receiving the pin 33. The pin extends through twodownwardly projected ears 34 and 35 on the ring 20.

The plunger 24 has a threaded end 26 on which a ring 21 of suitableferromagnetic properties is secured. It will be noted that the ring 21is held. a slight distance away from the top of the parts I! and I8 whenthe ring 20 is attracted, this distance being indicated by the numeral28. I may also use a spring 30 to aid in pushing the ring 20 away fromthe gap is. The spring 30 ismountedin two recesses 36 and 31 in thecylinder l6 and a head 29 on the plunger. The ring 21 preferably is ofthe same inner and outer circumferences as the ring 20 but it iscomposed of a material having a much higher Curie point, for examplepure iron.

In normal operation the ring 23 is placed in the position shown inFigure 2 so that it spans the gap l9 and engages with the inner surfacesof the parts It! and 13. The concentrated force of the magnet will holdthe ring 20 very securely. In other words, it will more or less lockring 23 in place. Now, however, if themember 20 is heated up in responseto a temperature change, or any other change which is reflected as atemperature change of the ring 20, to the Curie point temperature of thering, this ring 20 will then lose its magnetic property, that is, itwill I enter its paramagnetic state. The force of the spring 30 and theattraction of the ring 21 have been held in check by the attraction ofthe ring 20 to the parts l8 and I3, but when this attraction no longerexists due to the change in state of the ring 20, the ring 21 is drawntoward the gap l3 and this in turn forces the ring 20 away. Heating ofthe ring 20 beyond its Curie point destroys it as a bridge for themagnetic lines of force so these lines of force now tend to go to thering 21 and across the gap [9. As the ring 21 approaches the gap IS theclosing power is rapidly increased until the ring 2'! is in contact withthe parts l3 and I8. In other words, the gap 28 is reduced to zero. Thisdrives the Curie point ring 20 to the position shown in Figure 3.

The movement of the rod 24 in the manner Just described may be used tocorrect the change reflected by the heating of the Curie point metal 20.Since the force exerted by the spring 30 is greatest initially when thering 20 starts away from the parts l8 and i3 and the force of the ring21 is greatest when the ring is brought into engagement with the parts18 and I3, the ring and the spring cooperate to give a maximum forcemoving the rod 24 to the position indicated in Figure 3. The movementmaybe used to actuate any suitable kind of device for. the purposeintended. For example, it may be used to close an electrical circuit ifan alarm is to be given in that way, or it may be used to open a valveor to close a valve. The movement is non-recurring until two things havehappened. One of these is the cooling of the ring 20 until it is againbelow Curie point temperature, and the other is the application of asuitable force to move the ring 21 back to its original point. If anexterior force is applied to bring the ring 20 against the parts [8 andI3 before it hascooled below its Curie point temperature, the ring willnot stay in place. Therefore, it is impossible to re-set the deviceuntil the condition which heated the ring 20 is remedied. The ring 20,however, cannot return of its own accord to the position shown in Figure2. It must be pushed back by an exterior force overcoming the attractionof the ring 21 to the parts l8 and' I3.

This particular device has the advantage that it is extremely rugged andthat it can be placed in almost any kind of position without regard togravity or other forces because the magnetic attraction of a keepersealed across the gap 19 is so great that jolting, vibration and roughusage normally would have no effect thereon. If the whole unit isimmersed in or carried by the temperature producing material it willstill operate to move the plunger 24. Thus the device is capable ofbeing used under various conditions that normally rule out a great manycontrols.

In Figure 4 of the drawings, I show a modified construction wherein thenecessity for moving the Curie point member no longer exists. In thisform of the invention the various parts remain the same except for thefact that the Curie point member is placed directly in the gap l9, andthe movement of this member is not a part of the operation of thedevice. The Curie point member 20' in this form of the invention isshown as heated by fluid which is supplied to the member and taken fromit by conduits 38 and 39. In addition I provide for certain purposes aspacing member 40 around the plunger 24 to prevent the armature 21 frommoving into contact with the surfaces of the parts l2 and I3 andfreezing in that position.

The operation of the device shown in Figure 4 is essentially the same asthat shown in the other figures with the exception that the Curie pointmember 20' is stationary which acts as a valve on the magnetic lines offorce across the gap l9. When the member 20' is in a ferromagnetic statethe lines of force across the gap pass through the armature and have notendency to jump to the armature 21. However, if the member 20f isheated above its Curie point, it no longer serves as a good path for thelines of force, and the lines of force, therefore, jump to the next bestavailable path which is through the armature 21, and in so doing theyattract the armature 21 thus effecting operation of the plunger 24' toperform any control function that is properly spaced from the gap l9, itwill return to its original non-attracted position. It is, of course,necessary to have some means to normally hold the armature 21 in itsnon-attracted position. This may be a spring means, the weight of thearmature itself, or any desired equivalent means. If the device is soarranged that the armature 21 will automatically return to its normalposition when the member II is returned to its ferromagnetic state, thedevice then becomes an automatic re-set device that does not require anymanual control. It is believed to be evident that by proper balance ofthe 'force the device can be made manual or automatic merely by theremoval or insertion of the ring ll.

From the foregoing description it is believed that the nature andadvantages of my invention will be clear to those skilled in this art.

Having thus described'my invention, I claim:

1. A re-set type heat responsive actuator for indicating or controlmeans capable of operation in gas or liquid environment and positive inits operation, comprising a magnet, a highly permeable circuit thereforcomprising two ferromagnetic concentric members constituting oppositepoles for said magnet and separated from each other by a narrow circulargap, two armatures, one on each side of said gap and fixed to eachother, means mounting said armatures for movement axially with respectto the gap whereby either of said armatures may be brought into closejuxtaposition to the members and become a. magnetic shunt across thegap, one of said armatures having a Curie point much lower thantheother, and re-set means for moving the last named armature toengagement with said members.

2. A re-set type heat responsive actuator for indicating or controlmeans capable of operation in gas or liquid environment and positive inits operation, comprising a magnet, a highly permeable circuit thereforcomprising two ferromagnetic concentric members constituting oppositepoles for said magnet and separated from each other by a narrow circulargap, two armatures, one on each side of said gap and fixed to eachother, means mounting said armatures for movement axially with respectto the gap whereby either of said armatures may be brought into closejuxtaposition to the members and become a magnetic shunt across the gap,one of said armatures having a Curie point much lower than the other,and re-set means for moving the last named armature to engagement withsaid members, and spring means under tension between the core and thecarrier, and tending to move the first armature away from the gap.

3. A heat responsive actuator for indicating,

control, and similar purposes comprising a ring magnet, and highlypermeable rings at opposite sides of said ring magnet, one of said ringshaving an inner flange of reduced thickness providing a narrow annularpole face, a core on the other ring having a flange providing a narrowannular face in opposition to the first named pole face and spacedtherefrom to provide a definite gap in the magnetic circuit of saidmagnet, two armatures, one on each side of the gap between said polefaces and flxed to each other at a distance apart substantially greaterthan the pole face thickness whereby when one armature is injuxtaposition with the flanges the other is spaced therefromsufficiently to concentrate the magnetic lines of force in the closerone, one of said armatures being of a'material the Curie point of whichis at a temperature which, if the other armature were heated to suchtemperature would not seriously impair the ferromagnetic properties ofthe other armature.

4. A heat responsive actuator for indicating, controLand similarpurposes comprising a ring magnet, and highly permeable rings atopposite sides of said'ring magnet, one of said rings having an innerflange of reduced thickness providing a narrow annular pole face, a coreon the other ring having a flange providing a narrow annular face inopposition to, the first named pole face and spaced therefrom to providea definite gap in the magnetic circuit of said magnet, two annatures,one on each side of the gap between said pole faces and fixed to eachother at a distance apart substantially greater than the pole facethickness whereby when one armature is in juxtaposition with the flangesthe other is spaced therefrom sufliciently to concentrate the magneticlines of force in the closer one, a non-magnetic stem slidable endwisein said core and carrying said armatures, one of said armatures being ofa material the Curie point of which is at a temperature which, if theother armature were heated to such temperature would not seriouslyimpair :he ferromagnetic properties of the other armaure.

5. In combination an annular permanent magnet, ferromagnetic rings fixedto the ends thereof and extending inward, a ferromagnetic core securedto one of said rings and extending into the other ring, said core havinga peripheral flange within the other ring forming a. gap therewith, a

non-magnetic stem in said core and slidable endwise, and two armatures,one on each side of said gap carried by said stem, one of saidarrnatures having a lower Curie point than the other.

6. A temperature responsive device adapted for use as a control orindicating means comprising in combination a magnet, a highly permeablecircuit for said. magnet including a centrally disposed core and a ringabout said core, the ring and core having oppositely disposed facesproviding a main gap in the magnetic circuit, a Curie point membermounted in close juxtaposition with the ring and core at said gapwhereby to establish a magnetic shunt across said gap when the member isat a temperature below its Curie point, an armature adjacent to said gapand positioned to be attracted and moved toward thegap upon the memberlosing its ferromagnetic properties, and a mounting stem of nonmagneticmaterial fixed to the armature and slidable in the core to guide thearmature.

'7. A temperature responsive device adapted for use as a control orindicating means comprising in combination a magnet, a .highly permeablecircuit for said magnet including a centrally disposed core and a ringabout said core, the ring and core having oppositely disposed facesproviding a main gap in the magnetic circuit, a Curie 7 I 8 point metalarmature fixed in close juxtaposition REFERENCES CITED with the ring andcore in Sam gap whereby to The following references are 01 record in theestablish a magnetic shunt across said sap when file of this patent,

- the armature is at a temperature below its Curie magnetic properties.

point, a second armature adjacent to said gap 5 UNITED STATES PATENTSand positioned to be attracted and moved toward Number N Date the gapupon the first armature losing its ferro- 1,930,638 Oct 17' 19332,278,406 Serge Mar. 31, 1942 WITTMANN ROBERT 2,s39,oa'1 Mantz Jan. 11,1944

